A comprehensive regional investigation of the Eagle Ford Shale linking productivity to porosity-thickness (PHIH), lithology ([Formula: see text]), pore volume (PHIT), organic matter (TOC), and water-saturation ([Formula: see text]) variations has not been presented to date. Therefore, isopach maps across the Eagle Ford Shale play west of the San Marcos Arch were constructed using thickness and log-calculated attributes such as TOC, [Formula: see text], [Formula: see text], and porosity to identify sweet spots and spatial distribution of these geologic characteristics that influence productivity in shale plays. The Upper Cretaceous Eagle Ford Shale in South Texas is an organic-rich, calcareous mudrock deposited during a second-order transgression of global sea level on a carbonate-dominated shelf updip from the older Sligo and Edwards (Stuart City) reef margins. Lithology and organic-matter deposition were controlled by fluvial input from the Woodbine delta in the northeast, upwelling along the Cretaceous shelf edge, and volcanic and clastic input from distant Laramide events to the north and west. Local oxygen minimum events along the South Texas margin contributed to the preservation of this organic-rich source rock related to the Cenomanian/Turonian global organic anoxic event (OAE2). Paleogeographic and deep-seated tectonic elements controlled the variations of lithology, amount and distribution of organic matter, and facies that have a profound impact on production quality. Petrophysical modeling was conducted to calculate total organic carbon, water saturation, lithology, and porosity of the Eagle Ford Group. Thickness maps, as well as PHIH maps, show multiple sweet spots across the study area. Components of the database were used as variables in kriging, and multivariate statistical analyses evaluated the impact of these variables on productivity. For example, TOC and clay volume ([Formula: see text]) show an inverse relationship that is related to production. Mapping petrophysical parameters across a play serves as a tool to predict geologic drivers of productivity across the Eagle Ford taking the geologic heterogeneity into account.
Summary In a low-price environment, experts raise concerns about the economic viability of drilling in many locations across the Eagle Ford Shale play area. Although advances in drilling and completion technologies have helped to reduce the cost of production, reservoir quality still plays the pivotal role in drilling decisions. Eagle Ford reservoir quality is controlled by thermal maturity, which affects fluid composition, initial pressure, and petrophysical properties of the rock. This paper—which estimates original oil in place (OOIP), original gas in place (OGIP), and recovery factors (RFs) driven by reservoir quality—integrates geological and petrophysical analyses, fluid-properties characterization, and decline-curve analysis. For our petrophysical analysis, we calculated total organic carbon (TOC), lithology, porosity, pay-zone thickness, and water saturation for each square mile of the Eagle Ford play. We divided the play into 12 fluid regions on the basis of reported American Petroleum Institute (API) gravity and gas/oil-ratio (GOR) values and available temperature and pressure maps, developing a representative fluid model for each region to calculate a formation volume factor (FVF). The resulting OOIP and OGIP maps show regions of hydrocarbon accumulation. Our decline-curve forecast uses two-parameter scaling curves that are based on 1D, one-phase flow to predict the estimated ultimate recovery (EUR) of approximately 15,500 existing wells with at least 16 months of oil or gas production. We calculated oil and gas RFs for all the wells, and present a map of their distribution across the Eagle Ford play area. We generated OOIP and OGIP and RF distribution maps that help to improve the estimation of the amount of recoverable hydrocarbon. The maps reveal the areas with the greatest potential for recovery improvement as well as regions with high-recovery success. RFs calculated on the basis of EUR and well spacing are compared with a material-balance RF that is based on pressure and fluid properties. The Upper Eagle Ford can contribute to production, as indicated through RF plots.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.